Atmel SAM9X25, Manual

Page: 1047 / 1145

1047
11054A–ATARM–27-Jul-11
SAM9X25
1047
11054A–ATARM–27-Jul-11
SAM9X25
SA (MSB) 43
SA (LSB) 21
The sequence above shows the beginning of an Ethernet frame. Byte order of transmission is
from top to bottom as shown. For a successful match to specific address 1, the following
address matching registers must be set up:
• Base a 0x98 0x87654321 (Bottom)
• Base a 0x9C 0x0000CBA9 (Top)
And for a successful match to the Type ID register, the following should be set up:
• Base a 0xB8 0x00004321
45.4.7 Broadcast Address
The broadcast address of 0xFFFFFFFFFFFF is recognized if the ‘no broadcast’ bit in the net-
work configuration register is zero.
45.4.8 Hash Addressing
The hash address register is 64 bits long and takes up two locations in the memory map. The
least significant bits are stored in hash register bottom and the most significant bits in hash reg-
ister top.
The unicast hash enable and the multicast hash enable bits in the network configuration register
enable the reception of hash matched frames. The destination address is reduced to a 6-bit
index into the 64-bit hash register using the following hash function. The hash function is an
exclusive or of every sixth bit of the destination address.
hash_index[5] = da[5] ^ da[11] ^ da[17] ^ da[23] ^ da[29] ^ da[35] ^ da[41] ^ da[47]
hash_index[4] = da[4] ^ da[10] ^ da[16] ^ da[22] ^ da[28] ^ da[34] ^ da[40] ^ da[46]
hash_index[3] = da[3] ^ da[09] ^ da[15] ^ da[21] ^ da[27] ^ da[33] ^ da[39] ^ da[45]
hash_index[2] = da[2] ^ da[08] ^ da[14] ^ da[20] ^ da[26] ^ da[32] ^ da[38] ^ da[44]
hash_index[1] = da[1] ^ da[07] ^ da[13] ^ da[19] ^ da[25] ^ da[31] ^ da[37] ^ da[43]
hash_index[0] = da[0] ^ da[06] ^ da[12] ^ da[18] ^ da[24] ^ da[30] ^ da[36] ^ da[42]
da[0]
represents the least significant bit of the first byte received, that is, the multicast/unicast
indicator, and
da[47]
represents the most significant bit of the last byte received.
If the hash index points to a bit that is set in the hash register, then the frame is matched accord-
ing to whether the frame is multicast or unicast.
A multicast match is signalled if the multicast hash enable bit is set. da[0] is 1 and the hash index
points to a bit set in the hash register.
A unicast match is signalled if the unicast hash enable bit is set. da[0] is 0 and the hash index
points to a bit set in the hash register.
To receive all multicast frames, the hash register should be set with all ones and the multicast
hash enable bit should be set in the network configuration register.